1. Field of the Invention
The invention relates to an element for the thermal insulation of a building.
2. Background Description
In many cases the thermal insulation of a building is carried out by attaching thermal insulation elements to the exterior wall of the building. This can also often be carried out by retrofitting. The thermotechnical improvement of exterior walls is thus generally carried out with composite thermal insulation systems which have a thermal insulation in the form of polystyrene rigid-foam panels attached to the exterior wall on the outside. In the course of the thermotechnical improvement of a building, it is often useful not only to improve the insulation of the walls, but also to provide a controlled ventilation. Central ventilation systems necessary for this purpose often cannot be realized in existing buildings due to the low ceiling heights usually available and the enormous space requirements for ventilation ducts. The ventilation heat losses thus cannot be reduced as efficiently as transmission heat losses. It makes sense to carry out a retrofitting accommodation of ventilation systems only in buildings with high floor-to-floor heights. In this case suspended ceilings are installed, in which the ventilation ducts are accommodated. In buildings constructed after the second world war, the floor-to-floor heights are generally not sufficient for retrofitting suspended ceilings. In this case it has hitherto been possible only to realize decentralized systems that render possible a room-by-room supply with fresh air. However, the heat exchanger efficiency of systems of this type is much lower than the efficiency of central systems. The ventilation efficiency is also lower. Decentralized systems of this type are also expensive. The reason for this, among other things, is that a large number of fans are necessary. One starting point that is suitable in particular for retrofitting central ventilation systems is the accommodation of ventilation ducts in the exterior insulation. If thermal insulation is attached to the outside of the exterior wall in the course of the thermotechnical improvement of a building, ventilation ducts for a central ventilation system can be accommodated therein. To this end metallic spiral pipes are inserted into recesses made on-site in the exterior insulation at scattered intervals. For the interior area of buildings, ventilation ducts of rigid polystyrene foam are available with circular internal cross section and square external cross section. Suitably produced exterior insulation panels with integrated ventilation ducts and required sound-proofing properties do not exist as yet. A thermal insulation is known from JP 2004-060288 A2, which in individual areas has a hollow duct, through which air necessary for the ventilation can flow. This hollow duct is formed in that the generally thicker thermal insulation is composed of only a thin metal insulator in selected areas. The insulation element is therefore thinner in this area. When the insulation element is attached to the exterior wall, the said ventilation duct is formed between the metal insulation and the exterior wall.
DE 36 18 457 discloses a heat-insulating façade with an insulating layer, which is composed of insulating panels, arranged on the outside of the structure wall to be protected. A covering layer, in particular a plaster layer, is used to cover towards the outside. Ducts are provided in the insulating panels, which ducts run one next to the other in an approximately perpendicular or oblique manner and thereby follow the surface extension of the insulating layer. The ends of the ducts are open to the surroundings. The ducts are used to carry away undesirable moisture from the insulation. The resulting duct system does not have any connection to the interior of the building.